1. Field of the Invention
The present invention relates to an optical diffusion plate; particularly to a diffusion plate assembly with multiple microstructures thereon.
2. Description of the Prior Art
In recent times, a conventional cathode ray tube display apparatus is gradually replaced by the liquid crystal display apparatus, mainly due to the fact that the manufacturing cost of a liquid crystal display apparatus is remarkably reduced and a liquid crystal display apparatus emits lower radiation than a conventional cathode ray tube apparatus. In general, a liquid crystal display apparatus includes a backlight module assembly and a liquid crystal panel. The backlight module assembly is used to provide light for the liquid crystal display.
FIG. 1 shows a conventional backlight module assembly, the backlight module assembly 100 is comprised of cold cathode fluorescent lamps 110, a reflector 120, a diffusion plate 130 and pluralities of optical films 140. The cold cathode fluorescent lamp 110 is used to provide the light. The reflector guides the light, emitted from the spaced cold cathode fluorescent lamps 110, to the diffusion plate 130. The optical films 140 include a diffusion film 142 and a brightness enhancement film 144. In order to solve the problem of non-uniformity in brightness on the displaying surface of the liquid crystal panel, the diffusion plate 130 is placed to diffuse the light, emitted from the cold cathode fluorescent lamps 110, therefore providing a more uniform light emergence to the liquid crystal panel (not shown). Further, since pluralities of diffusion particles are disposed in the diffusion plate 130, the transmittance of the diffusion plate 130 is lowered. In general, the transmittance of the diffusion plate 130 is between 50% and 70%.
However, the problem in non-uniformity in brightness cannot be completely solved only by disposing the diffusion plate 130; therefore placing the diffusion film 142 on the diffusion plate 130 is necessary. Since the angle of light emergence is larger from the diffusion film 142, it is necessary to add the brightness enhancement film 144 on the diffusion film 142. The brightness enhancement film 144 is approximately between 0.062 mm and 0.375 mm. There are pluralities of prism-shaped structures 144a on the brightness enhancement film 144. The prism-shaped structures 144a can reduce the angle of the light emergence, so the brightness enhancement film 144 is able to condense the light, and the brightness can be enhanced in the viewing angle.
In general, compared to other elements in a backlight module assembly, the brightness enhancement film 144 is the most expensive. In order to reduce the whole cost of the backlight module assembly 100, the present invention aims to sustain the brightness even without the brightness enhancement film 144.